Bug 738356. Add JSAPI for doing the equivalent of Function.prototype.bind. r=jorendorff

js/src/jsapi-tests/Makefile.in

@@ -93,6 +93,7 @@ CPPSRCS = \
   testValueABI.cpp \
   testVersion.cpp \
   testXDR.cpp \
+  testBindCallable.cpp \
   $(NULL)
 
 CSRCS = \

js/src/jsapi-tests/testBindCallable.cpp

@@ -0,0 +1,27 @@
+#include "tests.h"
+
+BEGIN_TEST(test_BindCallable)
+{
+  jsval v;
+  EVAL("({ somename : 1717 })", &v);
+  CHECK(JSVAL_IS_OBJECT(v));
+
+  jsval func;
+  EVAL("(function() { return this.somename; })", &func);
+  CHECK(JSVAL_IS_OBJECT(func));
+
+  JSObject* newCallable = JS_BindCallable(cx, JSVAL_TO_OBJECT(func),
+					  JSVAL_TO_OBJECT(v));
+  CHECK(newCallable);
+
+  jsval retval;
+  bool called = JS_CallFunctionValue(cx, NULL, OBJECT_TO_JSVAL(newCallable),
+				     0, NULL, &retval);
+  CHECK(called);
+
+  CHECK(JSVAL_IS_INT(retval));
+
+  CHECK(JSVAL_TO_INT(retval) == 1717);
+  return true;
+}
+END_TEST(test_BindCallable)

js/src/jsapi.cpp

@@ -4631,6 +4631,14 @@ JS_IsNativeFunction(JSObject *funobj, JSNative call)
     return fun->isNative() && fun->native() == call;
 }
 
+JS_PUBLIC_API(JSObject*)
+JS_BindCallable(JSContext *cx, JSObject *callable, JSObject *newThis)
+{
+    RootedVarObject target(cx);
+    target = callable;
+    return js_fun_bind(cx, target, ObjectValue(*newThis), NULL, 0);
+}
+
 JSBool
 js_generic_native_method_dispatcher(JSContext *cx, unsigned argc, Value *vp)
 {

js/src/jsapi.h

@@ -4321,6 +4321,14 @@ JS_ObjectIsCallable(JSContext *cx, JSObject *obj);
 extern JS_PUBLIC_API(JSBool)
 JS_IsNativeFunction(JSObject *funobj, JSNative call);
 
+/*
+ * Bind the given callable to use the given object as "this".
+ *
+ * If |callable| is not callable, will throw and return NULL.
+ */
+extern JS_PUBLIC_API(JSObject*)
+JS_BindCallable(JSContext *cx, JSObject *callable, JSObject *newThis);
+
 extern JS_PUBLIC_API(JSBool)
 JS_DefineFunctions(JSContext *cx, JSObject *obj, JSFunctionSpec *fs);
 

js/src/jsfun.cpp

@@ -895,6 +895,22 @@ fun_bind(JSContext *cx, unsigned argc, Value *vp)
         argslen = args.length() - 1;
     }
 
+    /* Steps 7-9. */
+    Value thisArg = args.length() >= 1 ? args[0] : UndefinedValue();
+
+    JSObject *boundFunction = js_fun_bind(cx, target, thisArg, boundArgs, argslen);
+    if (!boundFunction)
+        return false;
+
+    /* Step 22. */
+    args.rval().setObject(*boundFunction);
+    return true;
+}
+
+JSObject*
+js_fun_bind(JSContext *cx, HandleObject target, Value thisArg,
+            Value *boundArgs, unsigned argslen)
+{
     /* Steps 15-16. */
     unsigned length = 0;
     if (target->isFunction()) {
@@ -910,23 +926,18 @@ fun_bind(JSContext *cx, unsigned argc, Value *vp)
         js_NewFunction(cx, NULL, CallOrConstructBoundFunction, length,
                        JSFUN_CONSTRUCTOR, target, name);
     if (!funobj)
-        return false;
+        return NULL;
 
     /* NB: Bound functions abuse |parent| to store their target. */
     if (!funobj->setParent(cx, target))
-        return false;
+        return NULL;
 
-    /* Steps 7-9. */
-    Value thisArg = args.length() >= 1 ? args[0] : UndefinedValue();
     if (!funobj->toFunction()->initBoundFunction(cx, thisArg, boundArgs, argslen))
-        return false;
+        return NULL;
 
     /* Steps 17, 19-21 are handled by fun_resolve. */
     /* Step 18 is the default for new functions. */
-
-    /* Step 22. */
-    args.rval().setObject(*funobj);
-    return true;
+    return funobj;
 }
 
 /*

js/src/jsfun.h

@@ -317,4 +317,8 @@ js_fun_apply(JSContext *cx, unsigned argc, js::Value *vp);
 extern JSBool
 js_fun_call(JSContext *cx, unsigned argc, js::Value *vp);
 
+extern JSObject*
+js_fun_bind(JSContext *cx, js::HandleObject target, js::Value thisArg,
+            js::Value *boundArgs, unsigned argslen);
+
 #endif /* jsfun_h___ */